The invention relates to a heating device of a substrate, comprising infrared radiation lamps designed to perform rapid thermal processing of the substrate inside a closed reaction chamber that comprises a transparent window wherethrough said infrared radiation passes.
Rapid thermal processing RTP and chemical vapour deposition RTCVD annealing processes generally make use of a furnace with infrared radiation generated by halogen lamps. The substrate, for example made of silicon in microelectronics product manufacturing technologies, is installed in a controlled atmosphere, in a closed enclosure, and the infrared radiation is directed onto the superficial face of the substrate through a transparent window.
The temperatures reached when the thermal processing operations are performed can be high, often over 1000xc2x0 C., with temperature gradients liable to reach several 100xc2x0 C./second. One of the important parameters of the processing is the uniformity of the temperature over the whole surface of the processed substrate, as the presence of thermal gradients of a few degrees centigrade between the central zone and the peripheral zone of the substrate can cause differences of quality on the substrate and/or homogeneity defects on the physical-chemical properties of the layers present at the substrate surface. The energy lost on the edges of the substrate is higher than for the center, which leads to a lower temperature at the edge than in the center.
To overcome these drawbacks in rapid thermal processes, it has already been proposed to compensate this temperature inequality by using the following known solutions:
a metal reflector positioned at the rear of the lamps,
heating of the two faces of the substrate with two sets of lamps arranged along the opposite sides of the reactor,
fitting a guard ring,
use of a susceptor,
rotating the substrate on a rotating plate,
association of two or more of the above solutions.
Implementation of these known solutions has not up to the present time enabled the light energy input at the surface of the substrate to be controlled perfectly according to the different thermal processing conditions used (annealing, growth, or thin layer deposition).
The document U.S. Pat. No. 5,790,751 describes a heating system with lamps arranged in vertical manner so that the lighting of eaandn lamp corresponds to a spot. The lamps are arranged in circular manner in a single assembly.
The document WO 00/34986 describes a quartz chamber that separates the lamps from the substrate.
The document U.S. Pat. No. 6,108,491 relates to spot lamps and not linear lamps. The spot lamps are arranged in circular manner under the substrate installed on a healing support (susceptor). The second series of lamps is arranged underneath, but over a smaller diameter to cover the central part of the heating support.
The document WO 00 30157 relates to two series of UV lamps with an arrangement on two fates of the reactor and an assembly at 90xc2x0.
The object of the invention is to achieve a heating device with controlled and directional infrared radiation designed to perform uniform rapid thermal processing of substrates of different geometries and dimensions.
The device according to the invention is characterized in that:
the infrared lamps are arranged in two superposed stages extending on a single side of the substrate, the lamps of the lower stage being arranged perpendicularly with respect to the lamps of the upper stage,
means for adjusting the supply power by groups of lamps achieve greater heating on the edges than in the centre of the substrate,
and a reflector in the form of a distribution grid is designed to reflect and channel the infrared radiation to control the power ratios between the different heating zones.
According to a preferred embodiment, the distribution grid of the reflector is formed by a criss-cross arrangement of strips bounding a plurality of compartments of variable cross-sections assigned to the heating zones. The power distribution per zone of the two stages of halogen lamps and the presence of the intercalated reflector enable uniform heating of the substrate to be obtained regardless of the geometry and dimensions thereof.
According to one feature of the invention, the strips are criss-crossed at right angles and are made of a material having an optimum reflection index to reflect the infrared rays. The material of the lamps may be metallic (steel or aluminum) or non-metallic (ceramic, zircon).
The infrared radiation lamps are halogen lamps and each stage advantageously comprises the same number of tubular lamps staggered at regular intervals and extending parallel to one another.
The reflector can be fitted between the lower stage of the lamps and the window or be fitted directly between the lamp zones so as to cover the height of the two series of lamps.